One of the biggest obstacles to confirming the impact of bisphenol-A (BPA) on human health is that the chemical is so ubiquitous in the environment — it is commonly used in plastics, dental fillings and sealants and in food and beverage can linings, among other places — that it is difficult to separate BPA’s influence from that of countless other factors. So researchers have mostly depended on in-vitro studies and on animal work to study BPA, and they have found some worrying results: BPA appears to interfere with the endocrine system and fertility and increase the likelihood of developing some cancers. Just because exposure to BPA may have these effects in animals, however, doesn’t necessarily mean the same thing is true in humans. But it is worrying.

Now a new study published in the journal Circulation focuses on humans, finding that BPA exposure may also be connected to an increased risk of heart disease. Using data from a long-running British health survey, researchers at the Peninsula College of Medicine and Dentistry, the University of Exeter and the European Centre for the Environment and Human Health found that people who had heart disease tended to have higher urinary concentrations of BPA. It’s hardly proof that BPA can cause heart disease, but it is the first study to indicate that exposure to the chemical may be correlated with an increased risk of heart problems, and the findings offer an important new route for research.

From David Melzer of the Peninsula Medical School, the leader of the study:

This study strengthens the statistical link between BPA and heart disease, but we can’t be certain that BPA itself is responsible. It is now important that government agencies organise drug style safety trials of BPA in humans, as much basic information about how BPA behaves in the human body is still unknown.

The study used data from the European Prospective Investigation of Cancer (EPIC), a long-term study that monitors the health of thousands of people in the British city of Norfolk. EPIC presents researchers with a wealth of data — including BPA concentration levels — and allows them to follow the subjects for years. For the Circulation study, scientists were able to track 758 initially health EPIC subjects who later developed cardiovascular disease, as well as 861 subjects who remained disease free. The results showed that the subjects who ended up with heart disease were more likely to have higher levels of BPA at the start of a 10-year follow-up period.

Again, this doesn’t show a clear causal relationship between BPA and heart disease. But given the sheer ubiquity of BPA, the results are just one more reason to keep looking at the chemical — skeptically.